Ultrasound-Guided Leukocyte-Poor Platelet-Rich Plasma For Partial-Thickness Tears Of The Rotator Cuff: Intralesional Injection

1. BACKGROUND: PARTIAL-THICKNESS TEARS OF THE ROTATOR CUFF

Partial thickness rotator cuff tears (PTRCTs) are a common pathology that may significantly impact a spectrum of patients including sedentary individuals, workers, and athletes (Matthewson et al., 2015). Based on cadaveric and imaging studies (Fukuda et al., 2000; Sher et al., 1995), the prevalence of PTRCTs ranges from 13% to 32%, in part, related to its strong correlation to patient age. In one magnetic resonance imaging (MRI) study of asymptomatic individuals (Sher et al., 1995), the overall prevalence of PTRCTs was 20%. In patients under the age of 40, the prevalence was approximately 4%; whereas, in patients over the age of 60, the prevalence was 26%. This age-related difference in prevalence was supported by other authors (Milgrom et al., 1995).

The etiology and pathogenesis of PTRCTs is likely multifactorial with both intrinsic and extrinsic factors contributing to an individual's rotator cuff lesion. Intrinsic factors, including age-related microscopic changes (hypocellularity, fascicular thinning, and granulation tissue) and decreased vascularity of the tissues, predispose a tendon to degenerative tearing and alterations in intratendinous strain (Matthewson et al., 2015; Sano et al., 1999). Extrinsic factors, including subacromial impingement, glenohumeral instability, and internal impingement can further contribute to anatomic pathology (Matthewson et al., 2015) Finally, traumatic events, either singular in nature or repetitive (e.g., overhead athlete), can eventually contribute to tensile overload and fiber failure of the rotator cuff. While still unclear, the presumption is that because of increased tendon strain due to the presence of a tear, PTRCTs generally increase in size over time (Bey et al., 2002).

2. ANATOMY OF THE ROTATOR CUFF: THE FIVE LAYERS OF THE HORSESHOE SHAPED SHOULDER ENGINE

The classical description of the rotator cuff involves a convergence of 4 tendons: supraspinatus, infraspinatus, teres minor, and subscapularis. These tendons form a multiple layered horseshoe shape flattened architecture which inserts onto the humeral head (Matthewson et al., 2015). When viewed from the glenohumeral joint, the superior insertion of the rotator cuff generally appears as a thickening of the capsule (the rotator cable) surrounding a thinner area of tissue (the crescent region), which inserts into the greater tuberosity. The rotator cable extends from the biceps anteriorly to the inferior margin of the infraspinatus tendon posteriorly. This thickening is thought to mechanically protect the weaker avascular crescent region where PTRCTs most commonly occur (Burkhart et al., 1993).

In 1992, Clark and Harryman demonstrated that the rotator cuff insertion contained 5 distinct histologic layers. The 1st layer comprised the superficial coracohumeral ligament. The 2nd and 3rd layers contain the tendinous fibers of the rotator cuff. The 4th and 5th layers consist of the arterioles and loose connective tissue adjacent to the bone. Although this horseshoe shaped insertion may have interdigitations between the rotator cuff tendons, there are separate footprints of each tendon, with a wide range of widths and lengths (Curtis et al., 2006). Curtis and others (Curtis et al., 2006; Ruotolo et al., 2004) described a relatively classic straight medial-to-lateral directional insertion of the rotator cuff tendon to bone (Figure 1(a)).

In 2008, Mochizuki et al. described a more curvilinear insertion of the infraspinatus tendon wrapping anteriorly around the superior aspect of the greater tuberosity. According to this description, the infraspinatus tendon consumes a large portion of the lateral aspect of the superior facet of the greater tuberosity, an area generally considered part of the supraspinatus tendon insertion. In contrast to classical descriptions of the rotator cuff, the supraspinatus tendon inserted on only a small portion of the most anterior aspect of the greater tuberosity and, in 21% of cases, fibers had inserted into the lesser tuberosity (Figure 1(b)) (Mochizuki et al., 2008; Matthewson et al., 2015).

3. PLATELET-RICH PLASMA CONCENTRATES: EFFECTS ON PARTIAL THICKNESS TEARS OF THE ROTATOR CUFF

A human platelet-rich plasma (PRP) concentrate can be defined as a preparation of autologous human plasma with increased platelet concentration, produced by centrifugation of a larger volume of a patient’s own blood (Ferreira-Dos-Santos et al., 2022). Platelets contain a plethora of growth factors in their α-granules: basic fibroblast growth factor one (bFGF-1), epidermal growth factor (EGF), hepatocyte growth factor (HGF), insulin-like growth factor one (IGF-1), platelet-derived growth factor αβ (PDGF-αβ), transforming growth factor β1 (TGF-β1), and vascular endothelial growth factor (VEGF). When preparing a PRP syringe, platelets are concentrated through the centrifugation process in order to then be injected in supraphysiologic concentrations to an injury site, with the final (theoretical) aim of augmenting the natural healing process (Ferreira-Dos-Santos et al., 2022).

During degranulation, a multitude of different growth factors is released from the α-granules of aggregated platelets, each playing a critical role in one or several steps of the healing process (Ferreira-Dos-Santos et al., 2022). As they bind to specific high-affinity transmembrane receptors, these growth factors trigger different intracellular signaling pathways. Some of the most important growth factors include bFGF-1, EGF, HGF, IGF-1, PDGF-αβ, TGF-β1, and VEGF. In addition, different chemokines, cytokines, and metabolites further supplement the action of these factors. Besides their influence on chemotaxis and cell migration via chemical mediation, growth factors also induce mitosis, contribute to the production of extracellular matrix (ECM), as well as mediate angiogenesis, promoting proliferation, maturation, and differentiation, ultimately leading to tissue repair (Ferreira-Dos-Santos et al., 2022).

A recent randomized controlled clinical trial showed that intralesional PRP can reduce the tear size in PTRCTs (Tanpowpong et al., 2023). Although subacromial steroid injection did not significantly affect the tear size and improved functional scores compared with baseline, PRP resulted in better improvement 6 months post-injection.

A recent 24-month retrospective clinical study showed that PRP is a safe and effective treatment for PTRCTs in patients who have failed conservative treatment of activity modification and physical therapy (Prodromos et al., 2021). In addition, better results were obtained in patients presenting with greater structural tendon damage compared with inflammation without structural damage.

4. HOW I DO IT: STEP-BY-STEP GUIDE TO THE TECHNIQUE UNDER ULTRASOUND-GUIDANCE

1. 80 cc whole blood collection. In patients over the age of 60-65, ideally use a system that allows for a variable initial whole blood collection, in order to draw up to 100-120cc, adjusted based on the patient’s age and/or comorbidities;
2. I prefer to use a double-spin system, aiming for an end volume of 4-5mL of leukocyte-poor platelet rich plasma (LP-PRP) for intralesional injection in tendon tears. Best practice guidelines suggest including an analysis of the final product using an automated cell counter tool (Figure 2).
3. I avoid local anesthetics in my needle trajectory, given their potencial deleterious effects on platelet activation (reported in vitro, not in vivo - controversial). Instead, I perform a pre-procedural suprascapular nerve block (through a posterior approach) using 4-5mL of lidocaine 2%. This ensures the patient stays comfortable throughout the whole procedure.
4. I perform the procedure with the patient in the lateral decubitus position. This provides me with additional hand support during the whole technique, improving my needle-probe coordination.

5. DEMONSTRATION OF THE TECHNIQUE: VIDEO UNDER REAL-TIME ULTRASOUND-GUIDANCE

In the video (using a FUJIFILM Sonosite Europe PX equipped with a L12-3 MHz Linear Probe, at Hospital Clínic de Barcelona):

Positioning of the needle tip (22G 50mm Sonoplex II, PAJUNK?) and administration of intralesional LP-PRP in an active male patient in his 60s, presenting with an Ellman II articular partial-thickness tear of the supraspinatus tendon, previously confirmed by magnetic resonance imaging.

Legend: Ac - Acromion; Del - Deltoid muscle; HH - Humeral head; L - Lateral; M - Medial; SS - Supraspinatus tendon. Initial test injection showed backflow with the needle tip still within the most superficial tendon fibers. After a small adjustment, correct final position of the needle tip was confirmed by real-time spread of the injectate within the lesion.

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